A3.1 - SL PT 2

Genetic Diversity and Chromosome Characteristics
  • Chromosomes and Species:
    • All living organisms organize their DNA into chromosomes; this is a common characteristic.
    • Each species has a specific number of chromosomes:
    • Humans: 46 chromosomes
    • Watermelon: 22 chromosomes
    • Goats: 60 chromosomes
    • The number of chromosomes does not correlate with the complexity of the organism.
Evolution from a Common Ancestor
  • Chromosome Variation Theory:
    • Evolutionary biology proposes that different species can retain unique chromosome numbers.
    • Hypothetical scenario: an organism starts with 2 chromosomes. If a chromosome gets separated, this could lead to species evolving with different chromosome counts over time.
Karyograms and Karyotypes
  • Understanding Karyograms:
    • A karyogram is a pictorial representation of an organism's chromosomes.
    • Karyotype: characteristics of chromosomes in a species based on the karyogram.
    • Human karyogram appears with 46 chromosomes, often analyzing males with X and Y chromosomes.
  • Creating Karyotypes:
    1. Cell Selection: Identify a cell in mitosis.
    2. Staining Cells: Use stains that attach to DNA.
    3. Cell Lysis: Burst the cell to analyze chromosomes.
    4. Organization: Arrange chromosomes based on centromere position and size.
Definitions in Genetics
  • Genome:
    • Complete set of genetic information in an organism, consisting of all base sequences (A, T, G, C).
  • Gene:
    • Segment of DNA that encodes for a protein (e.g., a gene for blood type).
  • Unity in Species:
    • Organisms of the same species have the same genes in the same chromosome locations.
  • Diversity within Species:
    • Variation in alleles (different base sequences) for the same gene among individuals of a species.
  • Single Nucleotide Polymorphisms (SNPs):
    • Positions in DNA where individuals may differ in a single nucleotide, responsible for variation in traits.
    • Approximately 5,000 SNPs among 3 billion base pairs in human DNA.
Comparison of Genetic Information
  • Diversity Across Organisms:
    • Two different organisms, such as goats and apples, can exhibit significant differences:
    • Different genome sizes or numbers of genes.
    • Variations in base sequences within identical genes.
  • Quantifying Genome Size:
    • Methods to quantify genome size:
    • By mass (not practical due to small DNA mass, e.g., humans: 6 picograms)
    • By number of base pairs (e.g. humans: 3,200,000,000,000 base pairs)
Advances in Genomic Sequencing
  • Evolutionary Relationships and Sequencing:
    • Genome sequencing has improved significantly, enabling faster and cheaper analysis of different organisms.
    • This advancement can modify our understanding of evolutionary relationships, potentially changing previous classifications.
  • Applications of Genomic Knowledge:
    • Can contribute to personalized medicine and understanding diseases based on genetic information.
    • Identifying how different genes influence drug effectiveness, such as pain medication.
  • Potential for Future Discovery:
    • Ongoing genomic research presents opportunities for innovative applications and insights in biology, healthcare, and beyond.